The present invention relates to a system for liquid cleaning a plurality of dirty cylindrical paper air filters by subjecting each filter to a cleaning cycle including successive first, intermediate and final cleaning steps, each step using cleaning liquid from a different source.
In prior art systems filter cleaning has been accomplished by recycling a continuous flow of a clean water with resulting effluent becoming increasingly contaminated over a period of time.
Prior art filter cleaners have used compressed air as well as continuous streams of fresh cleaning liquid or have continuously recycled a stream of cleaning liquid from a large reservoir usually provided with sufficient volume to enable settling of particles from the liquid after it rinses a filter. Maintenance and cleaning of such a large settling system is both labor intensive as well as requiring a large area for installation. Such a large system poses additional problems as to portability.
Prior art filter cleaning systems have used relatively high-volume water passed continuously over and through the filter media in order to remove the particulate matter which is built up on the filter surfaces and which may have become caked in place. The initial removal is primarily a mechanical function in which the flow water is used to dislodge the cake and accordingly the water which is used for this purpose need not be free of particulate matter prior to its coming into contact with the particular filter to be cleaned.
The present invention utilizes for each of the cleaning steps in a filter cleaning cycle, except for a last fresh water cleaning rinse step, water which has been saved as the partially contaminated effluent of a xe2x80x9ccleanerxe2x80x9d or later step in the sequential steps of a preceding filter cleaning cycle. By recycling the water accordingly the present system reduces the amount of stored water in the system and because of the reduction in size of the required storage tanks the system can be made relatively portable, as by mounting on a truck.
Moreover the present system can be directly connected to a domestic water system for obtaining fresh water as well as for discharge of non-hazardous effluent from the system to a domestic sewer system.
The present system enables high volume flow rates for each step of the cleaning cycle even when a domestic water source can provide only a substantially lower rate of input to the system.
Control components for three pumps, a filter rotating motor and several valves to sequentially operate the steps, or timed portions of steps, of each filter cleaning cycle and selectively control the spraying of different outside and inside filter surfaces are relatively simple and easily configured for either manual or completely automatic time controlled sequenced operation of all components upon mere initiation of a cycle by the user after loading the cleaning station with one or more coaxially arranged filters to be cleaned.
Although the prior art rotated cylindrical filters about their axes with the axes inclined during filter cleaning operations, the prior art has not recognized or suggested the improvement achieved by the present invention in sequencing several distinct spraying steps in a single cleaning cycle and availing of the use of inclination of the filter axis to facilitate flowing and collecting all of the different mixtures of cleaning liquid and entrained contaminants as effluents during each of the steps of the cleaning cycle. Inclined rotational support for the filters is achieved in a manner well known in the art by using motor-driven parallel rollers engaging the outer cylindrical surface of each filter and includes conventional shoulders engaged by the lower end of the roller to prevent axial movement of the filter during cleaning.
Nozzles are positioned to direct selected flows of cleaning liquid to the interior and exterior surfaces of the filter cartridge. The nozzle locations are such as to avoid interference with loading and unloading filters being cleaned at the cleaning station Typically a dirty filter has a xe2x80x9ccleanxe2x80x9d side and a xe2x80x9cdirtyxe2x80x9d side. It is desirable to avoid introducing any contaminants to the clean side and therefore an initial application of contaminated liquid is used only on the xe2x80x9cdirtyxe2x80x9d side and serves the function of knocking the accumulated dust cake from the dirty filter surface.
In the present system the initial cleaning cycle step using application of water primarily to dislodge the accumulated xe2x80x9cdust cakexe2x80x9d from the surface of the filter obtains the water from a storage tank of used or unclean water collected during an earlier intermediate step of the preceding filter cleaning cycle, whereas subsequent cleaning steps in one cleaning cycle are effected using progressively cleaner cleaning liquids.
In the preferred embodiment the entire cleaning cycle comprise three stages or steps and for each stage a separate reservoir is provided. A xe2x80x9ccleanxe2x80x9d tank is filled with clean water such as that derived from a domestic water source. The clean tank provides water for the final cleaning stage during which the effluent is captured for retention, filtered, and sent to a xe2x80x9cfiltered tankxe2x80x9d. The effluent of the final rinse step is relatively uncontaminated and can be filtered using a simple auxiliary string wound cartridge filter without posing any significant problem of clogging of the filter.
While it would be possible in to eliminate the clean tank and provide a source of water directly from the domestic source for the last cleaning stage, typically the flow rates available from the domestic source are not sufficient to match the flow rates desirable for the present invention. Accordingly by providing a reservoir for storage of the clean water the inflow of domestic water can be maintained into the reservoir through the entire cycle and during idle periods at the cleaning station even though the higher flow rate from the clean tank only occurs during, for example, one-third of the cleaning cycle. In this manner even though the instantaneous incoming flow rate of clean water from a domestic system may be inadequate for efficient cleaning of the object to be cleaned, the overall flow rate over time is sufficient to meet the needs of the present device.
The flow of cleaning liquid during each step of the cleaning cycle is maintained by a pump which for example provides a flow of approximately 50 gallons per minute. Using a system of storage reservoirs and manually or automatically controllable valves, water is circulated in a sequence which provides progressively cleaner water for the cleaning process.
The process runs relatively continuously and provides little time for settling of the many suspended particulates in any one of the reservoirs. The reservoir for the first stage accumulates the dirtiest water and a centrifugal separator and drain means are provided at the bottom of the reservoir to allow removal of any accumulated sediments. Each of the other tanks need only be provided with a means for draining contaminants from the bottom of the tank.
The greatest benefits of the present invention are achieved by removal and disposal of a relatively high percentage of the particulates in the initial step of the filter cleaning cycle.
The present system uses a multi-stage cycle for cleaning a filter at a cleaning station with each successive stage using a cleaning liquid which is cleaner than that used in the preceding stage. A supply reservoir for each stage obtains its cleaning liquid either from a fresh cleaning liquid source or from effluent of a respective later stage of a preceding operating cycle at the cleaning station.
Each cleaning cycle takes about three minutes followed by an idle period of the cleaning station of not more than three minutes for servicing and reloading the cleaning station with dirty filters to be cleaned. Thus a total time of perhaps six minutes is available for supplying an input storage reservoir with clean cleaning liquid at a rate which is substantially lower than the rate of flow of the cleaning liquid during each cleaning cycle stage which may be as high as 50 gallons per minute.
The reservoir containing the dirtiest cleaning liquid after the first stage of the cleaning cycle may be equipped with a centrifugal separator for solid particles at the bottom of the reservoir to separate and remove some of the contaminate particles before the cleaning liquid of this reservoir is used in a succeeding cleaning cycle. An outlet at the bottom of this reservoir with suitable manually or automatically controlled valve means and pump facilitates removal of such separated material to an appropriate disposal site.
The present invention recognizes the utility of saving dirty water from an earlier cleaning cycle for such initial cleaning and using cleaner water for the ensuing steps particle removal. Such reuse of cleaning liquid minimizes the amount of liquid stored in the system for a cycle of operation to clean a filter at the cleaning station. Thus the system may be readily portable and is suitable for direct connection to a domestic water system both for obtaining fresh cleaning liquid as well as for disposing of dirty cleaning liquid via the sewer line of the domestic water system. The present system enables high volume flow rates of the cleaning liquid during each step of the cleaning cycle notwithstanding only low volume capability of the domestic water supply.
Among the objects of the invention is to provide a multistage liquid cleaning system for filters which can use large volumes of cleaning liquid and still be portable by truck in a usable configuration.
Another object of the invention is to provide a liquid cleaning system which can be connected to a domestic system for supply of fresh water and for disposal of waste effluent to a domestic sewer line.
A further object of the invention is to achieve high volume liquid flow rates in a liquid cleaning system which substantially exceed the liquid flow rates available from a source of fresh liquid such as a domestic water system.
Another object of the invention is to enable recycling of cleaning liquid to different stages of cleaning in successive filter cleaning cycles.
Another object of the invention is to provide a multi-stage cleaning system in which each successive stage of cleaning of a filter uses a progressively cleaner cleaning liquid.
Another object of the invention is to provide a multi-stage cleaning system in which each successive stage of cleaning of a filter except the last uses a recycled partially contaminated liquid collected during a stage of a preceding cleaning cycle
Another object of the invention is to enable partial removal of contaminant particles from a filter cleaning effluent before using this effluent for further filter cleaning in a succeeding cleaning cycle.
A further object of the invention is to reduce the time required for liquid cleaning of filters by improved control of sequential filter cleaning steps in a multi-step process using different recycles liquids.